(1) Field of the Invention
The invention relates to a method of metallization in the fabrication of integrated circuits, and more particularly, to a method of tungsten metallization preventing peeling of the tungsten or underlying glue layer called the volcano effect in the manufacture of integrated circuits.
(2) Description of the Prior Art
Tungsten-plug metallization is well-known in the art. A conventional tungsten plug process of the prior art is illustrated in FIGS. 1 and 2. Referring now to FIG. 1, there is shown semiconductor substrate 10. A contact hole 22 has been opened through interlevel dielectric layer 20 to source/drain region 14. A glue layer composed of titanium layer 24 and titanium nitride layer 26 has been deposited over the surface of the substrate and within the contact hole. Referring now to FIG. 2, a layer of tungsten 28 is deposited which will form a plug within the contact hole. 30 illustrates the volcano effect. The tungsten or the titanium nitride layer will peel away from the substrate. When tungsten is blanket deposited, the tungsten hexafluoride (WF.sub.6) precursor penetrates the titanium nitride film and reacts with the titanium according to the following reaction: EQU 2Ti+WF.sub.6 .fwdarw.W+2TiF.sub.3
The TiF.sub.3 is a nonadherent layer and will cause the tungsten or the titanium nitride to peel.
U.S. Pat. No. 5,175,126 to Ho et al teaches "stuffing" the titanium nitride grain boundaries with oxygen or nitrogen reaction products using an atmospheric annealing process in order to improve the integrity of the titanium nitride layer. U.S. Pat. No. 5,173,450 to C. C. Wei uses amorphous silicon between two titanium layers in which the amorphous silicon acts as the origin of silicon used to form TiSi.sub.2 instead of the silicon's coming from the source and drain regions.